The production of paper from pulp to finished paper may be composed of several sequential winding and unwinding stages in which the continuous paper web passed from the preceding processing stage is reeled around a reel spool to form a machine reel, and this machine reel is unwound again at the unwinding stage to pass the paper web to the next processing stage. A typical example is a so-called off-line production of coated paper grades, in which in the paper production line i.e. in the paper machine a continuous web of several meters in length is produced from fibrous pulp, which web is reeled in the reel-up in the terminal end of the paper machine to form a machine reel. Several reel-ups have been presented in the patent literature, and reference can be made for example to the European patents 483092, 483093 and to the international patent publication WO 95/34495. In such winding stations a continuous web passed from the preceding sections of the machine is reeled around a reeling axle i.e. a reel spool, which is a roll of several meters in width, dimensioned with respect to the size of the reel in a suitable way and supported in the winding station by its ends with a suitable supporting structure. The winding stations operate continuously, wherein a new reel spool is brought to the reeling station without reducing the speed of the preceding machine, and the paper web is guided around a new reel spool by using change methods for which numerous patented solutions have been developed. Similarly, patented solutions have been developed for the ways of arranging a loading (linear load) between the reeling cylinder guiding the web and the reel.
In the unwind, the machine reel reeled in the preceding stage is unwound, and a winding station of this type is presented for example in the Finnish patent 100323 and in the corresponding U.S. Pat. No. 5,709,355. The unwind of a coater presented herein operates continuously, wherein a new machine reel which is brought to the unwind is joined at full speed to the paper web of a machine reel that is becoming empty, by means of a splicing device. The unwind is used in the beginning of off-machine coaters to lead the web wound up in the preceding winding station from the successive reels to the coating process. The preceding winding station can be a so-called rereeler in which the reel reeled in the reel-up of a paper machine is unwound and wound up to form a reel which is suitable for the finishing process.
In the end of the off-machine coater there is again a reel-up in which the paper web passed from the coater is reeled around the reel spool again to form a machine reel.
In order to implement the continuous operation, the change of the reels in the reel-up and in the unwind should proceed without problems, and these functions are the most critical stages in the continuous winding up or unwinding. Because of this, it would be advantageous to produce machine reels as large as possible to reduce the number of changes. This is restricted by the heavy weight (several tens of tonnes, in wide machines typically over 50 tonnes) of the reel, and the existing constructions which are dimensioned for particular maximum diameters of the machine reel.
Heretofore, attention has been paid to single winding processes (winding up, unwinding) and their problems.
Conventionally, in lines producing coated paper grades, for example in an LWC-paper line provided with a separate coater, machine reels of equal size are reeled in the reel-up of the paper machine and thereafter in each reel-up process in accordance with the requirements set for the customer rolls of the slitter-winder.
Especially in lines producing coated paper grades, as for example the above-mentioned LWC line, it is difficult to modernize the winding stations in such a way that the diameter of the reel is increase throughout the entire line, because in that case all the reel-up unwinds, cranes, reel spools (nearly 100 by number) and storage rail arrangements have to be modernized. Similarly, inside a factory the lifting height might restrict the growth of the diameter at some points. Thus, when compared to the attained advantages, it is not lucrative to increase the diameters of the reels, even if new winding station constructions provided the possibility for this.